Projectors are used to reproduce a larger image on a projecting screen by projecting light beam and widely used for presentation in meeting and tuition. The content displayed by projectors are gradually changed from dull still slide to more vivid animated graphic. Moreover, the projectors gain much progress in weight, size and resolution.
The commercially available projectors are listed below.
1. Overhead Projector
This is an old-fashion type projector used to display transparency. The transparency is generally prepared by using a printer, which is a time consuming job.
2. Slide Projector
This is another old-fashion type projector used to display slide, which has better resolution and color. However, slides also should be prepared in advance. This is also a time consuming job and no animated effect is available.
3. CRT Projector
This projector employs three electron guns to project light beams of three primary colors and can provide animated effect. However, the CRT projector is bulky and of high cost. Therefore, the CRT projector is generally used in meeting room and audiovisuals application.
4. LCD Panel and Spot Light Projector Assembly
The LCD panel is used to display image from a computer and the spot light projector is used to project the image to a screen. When being stand-alone, the spot light projector can be used as a slide projector. However, the overall assembly is still bulky.
5. Single Gun CRT Projector
The single gun CRT projector is mainstream product with easy maintenance, easy operation, high brightness and portability. However, the prices of the single gun CRT projector are greatly deviated by its brightness specification and resolution.
Moreover, the existing single gun CRT projector is used with computer and now reflective LCD type unit and digital signal processing type unit are available.
However, the above-mentioned projectors are not stand-alone unit and should be used with computer, for example, desktop computer, notebook computer or palm computer. Moreover, the existing projectors do not have network function.